Lactation curves and effect of pup removal on milk fat of C57BI/6J mice fed different diet fats

Abstract

Groups of C57BI/6J mice, fed either acis (C-Diet) ortrans diet (T-Diet) were milked without preconditioning at 6, 8, 10 and 12 dayspostpartum. On day 10, groups of mice were also milked 4, 6 and 18 h after separation of the pups. Except for the 18-h separation, all T-Diet fed animals produced milk of lower fat content than did the C-Diet animals (P<0.001) throughout the lactation period measured. In the C-Diet mice, the 6-h separation period resulted in a decrease (P<0.03) in fat, but the diet-depressed milk fat of T-Diet animals was not decreased further until the 18-h separation period. Milk volume increased as lactation progressed and was greatly increased as a result, of preconditioning (P<-0.001), even at 4 h of separation when fat was not reduced, and was always greater for T-Diet animals. Within diet groups, fatty acid composition was similar throughout the lactation period studied and was not affected by preconditioning, except in the 18-h separation period, whende novo fatty acids were significantly reduced (P≤0.05). The data are consistent with the hypothesis that preconditioning results in lowered milk fat values and that preconditioning techniques can explain discrepancies in literature values for murine milk fat.